Proposed Control Protocol Research Articles

Fixed-time leader-following/containment consensus for a class of nonlinear multi-agent systems

This study focuses on the fixed-time leader-following consensus problem for a class of multi-agent system with multi-dimensional nonlinear dynamics. First, the distributed static fixed-time control protocol is put forward to settle this issue. Different from the existing fixed-time control methods, the proposed control protocol is continuous such that the chattering phenomenon can be avoided. Note that the proposed static fixed-time controller is dependent on the global information of network topology. To address above issue, the fully distributed adaptive fixed-time controller is further proposed. Moreover, the results in fixed-time leader-following consensus are extended to containment consensus. And the case of directed graph is also considered. Finally, several examples are provided to illustrate the feasibility of the theoretical results.

Fuzzy adaptive finite-time consensus tracking control for nonlinear multi-agent systems

This paper focuses on the finite-time consensus tracking control problem of nonlinear multi-agent systems. Dynamics of each agent has completely unknown nonlinear terms that cannot be directly used for control design. Therefore, fuzzy logic systems are employed to approximate these nonlinear functions. Furthermore, a finite-time fuzzy adaptive consensus tracking protocol is proposed for a class of nonlinear multi-agent systems by using integral-type Lyapunov functions. The developed adaptive backstepping design scheme successfully avoids the singularity problem of the derivatives of virtual control signals. It is shown that with the presented control protocol, the consensus tracking errors converge to a small neighbourhood of the origin in finite time, and the other signals of multi-agent systems are bounded. Finally, a numerical example is used to verify the effectiveness of the proposed control protocol.

Fixed-Time Formation Control of Unicycle-Type Mobile Robots With Visibility and Performance Constraints

This article presents a fixed-time leader-follower formation control protocol for a swarm of unicycle-type mobile robots with visibility and performance constraints. Under a vision-based formation control framework, mobile robots calculate their control signals with only the local relative distance and bearing angle provided by onboard stereo or RGB-D cameras. Since the sensing capability of the fixed onboard cameras is subject to limited range and angle of view, the field-of-view constraints are considered to ensure that each follower can always detect its leader and meanwhile avoid collision with the leader. The time-varying and asymmetric performance constraints on formation tracking errors are applied to guarantee the transient and stead-state performance. Furthermore, the proposed control protocol can be extended to address the control design problem without constraint requirements. Based on the fixed-time control design and Lyapunov analysis, formation tracking errors are shown to converge to a small neighborhood of zero in fixed settling time. Simulation and experiment studies are performed to illustrate the effectiveness of the formation control protocol.

Containment control of general linear multi-agent systems by event-triggered control mechanisms

This paper discusses the containment control (CC) problem of general linear multi-agent systems (MAS)s by means of two kinds of distributed event-triggered mechanisms. Two types of event-triggered control protocols, namely, the state feedback control law and the dynamic output feedback control protocol, are designed for each follower. Under the proposed control protocols and triggering mechanisms, the containment control problem can be solved by proving that the containment error converges to zero based on the assumption and algorithms. At last, we verify the rationality of the theoretical results. Through two numerical simulation, we can see that the trajectory of each follower converges to the convex hull formed by all leaders. In addition, in order to verify the advantages of the obtained results, we give a simulation example and compare the methods designed in this paper with the methods in other literature.

Distributed control of multi-agents system via static feedback controllers under directed networks

During recent years, a lot of distributed control approaches based on static feedback controllers have been proposed to realize consensus of multi-agents systems with undirected topologies. However, many of these approaches have not been generalized to systems with directed topologies yet. Therefore, in this paper, for first- and second-order multi-agents systems with directed topologies, we propose a series of new nonlinear consensus protocols based on traditional design. With integral Lyapunov functions, we can prove the stability of proposed control protocols and a group of simulation results are also given to testify our theory.

Prespecified-time synchronization of switched coupled neural networks via smooth controllers

This paper considers the prespecified-time synchronization issue of switched coupled neural networks (SCNNs) under some smooth controllers. Different from the traditional finite-time synchronization (FTS), the synchronization time obtained in this paper is independent of control gains, initial values or network topology, which can be pre-set as to the task requirements. Moreover, unlike the existing nonsmooth or even discontinuous FTS control strategies, the new proposed control protocols are fully smooth, which abandon the common fractional power feedbacks or signum functions. Finally, two illustrative examples are provided to illustrate the effectiveness of the theoretical results.

Prescribed-time cluster lag consensus control for second-order non-linear leader-following multiagent systems

Prescribed-time Lag consensus, as a special case of prescribed-time cluster lag consensus, is first investigated. The task is to design a control protocol for each follower so that the multiagent system (MAS) achieves lag consensus in any specified time. To achieve this goal, we propose a new distributed controller, in which the control gains are designed as time-varying functions related to the pre-specified time. In addition, a state transformation is introduced to tackle the technical difficulty caused by time-varying functions of different powers in the theoretical proof process. Then, a solution for the cluster lag consensus problem of the MAS is provided, so that under the proposed control protocol, each subsystem composed of followers from the same group and the leader achieves lag consensus with a different lag time in the specified time. By using a state transformation, Graph theory and generalized Lyapunov stability theory, the validity of the designed schemes is verified theoretically and sufficient conditions for the two conclusions are given respectively. Finally, we give two simulation examples to show performances of the proposed solutions.

Observer-Based Bipartite Containment Control for Singular Multi-Agent Systems Over Signed Digraphs

This paper aims at solving the bipartite containment problem for linear singular multi-agent systems (MASs) with multiple dynamic leaders over general signed digraphs, where each leader can be autonomous or dynamically evolving via interactions with its neighboring leaders. To this end, we first establish some properties for the Laplacian matrices of signed digraphs. Then, three distributed observer-based bipartite containment protocols are proposed using different local output information. Multi-step algorithms for constructing the corresponding proposed protocols are also given. It is shown that under the proposed control protocols, bipartite containment can be achieved for any admissible initial states provided that the underlying signed digraph is weakly connected. Compared to the existing related works, the major contribution of present work is that the developed results are applicable for arbitrary weakly connected signed digraphs, no matter whether they are sign-symmetric or sign-asymmetric and whether they are structurally balanced or unbalanced. Two numerical examples are finally given to demonstrate the validity of our results.

Adaptive controller design for fixed-time leader-following consensus of multi-agent systems with discontinuous dynamics

This paper investigates the adaptive fixed-time consensus of a class of multi-agent systems with discontinuous dynamics. First, under the framework of Filippov solutions, a new theorem is established to achieve fixed-time consensus of discontinuous multi-agent systems using the proposed control protocol. Furthermore, an adaptive control protocol is provided in the second theorem that highly improves the control signals of the system. Finally, numerical simulations are worked out to illustrate the effectiveness of our theoretical results.

Prespecified‐time distributed synchronization of Lur'e networks with smooth controllers

AbstractInstead of estimating the upper bound of the settling time in traditional finite‐time control methods, this paper considers the prespecified‐time synchronization of Lur'e networks, in which the settling time can be preset according to the requirement of tasks. Some smooth controllers are designed to achieve the goal of synchronization in a prespecified time and to maintain the synchronization after that. In addition, without the help of signum function or fractional power state feedback, the proposed control protocols are based on regular feedback and are smooth everywhere. Finally, two numerical examples with Chua's circuits are carried out to substantiate the effectiveness of the proposed designs.

Time-Varying Formation Control of General Linear Multi-Agent Systems Under Markovian Switching Topologies and Communication Noises

This brief studies the time-varying formation (TVF) control of linear multi-agent systems (MASs), where the communication topology switches from several different topologies and the switching signal is depicted by a right-continuous Markov process. The communication noises are taken into account simultaneously, which are described as independent white noises with noisy intensities. A class of stochastic-approximation type control protocols is given and certain sufficient conditions are derived for realizing the TVF stabilization in mean square sense. Moreover, the indicative function and infinitesimal generator are imported in Lyapunov functions to help proving that the MASs can be formed into stable TVF shapes with the proposed control protocols. In the end, an simulation example is performed to state the availability of the approach.

Robust finite-time and fixed-time bipartite consensus problems for multi-agent systems via discontinuous protocol

This paper addresses the robust finite-time and fixed-time bipartite consensus problems for multi-agent systems under the signed graphs. A unified discontinuous control protocol is constructed to achieve both finite-time bipartite consensus (FINBC) and fixed-time bipartite consensus (FIXBC) only by adjusting the parameters, regardless of whether the signed graph is structurally balanced or unbalanced. By using discontinuous techniques, some simple sufficient conditions for FINBC/FIXBC are provided; moreover, the upper bounds of the settling times are explicitly estimated. Simulations show that the proposed control protocols are effective.

Distributed leaderless synchronisation control for non‐linear MASs with both parameter and non‐parameter uncertainty terms

In this study, the authors first discuss the adaptive synchronisation control for discrete-time non-linear multi-agent systems (MASs) with parameter and non-parameter uncertainty terms under leaderless strongly connected digraph, which has not been mentioned in the existing literature. To cope with these two kinds of uncertainties, a state variable is used as an auxiliary tool to compensate for the non-parameter uncertainties, meanwhile, a new dead zone is constructed to ensure the boundedness of the estimated values of the unknown parameters. Based on the local information within the neighbourhood, distributed adaptive synchronisation protocols are designed. Moreover, they strictly prove that the designed adaptive control protocols can harmonise all agents' dynamics to achieve their synchronisation in theory. At the end of this study, an example is provided to indicate the validness of the proposed control protocols.

Distributed adaptive containment control for a class of discrete-time nonlinear multi-agent systems with unknown parameters and control gains

This paper considers the containment control problem for the discrete-time nonlinear multi-agent systems with unknown parameters and completely unknown control gains. In this paper, the dynamics of each agent are nonlinearly coupled with the neighbors’ states. To deal with the unknown parameters and control gains, a projection-type estimation algorithm is designed with the singular value avoided in the estimated control gains. The bounded estimation errors of parameters and control gains are guaranteed by the convergence analysis based on the Lyapunov approach. Then, using the estimated parameters and control gains, a distributed adaptive control protocol with only local information is designed for multi-agent systems. Under the proposed control protocol, the containment of multi-agent systems is guaranteed from a novel viewpoint of the absorbing Markov chain. Furthermore, simulations are carried out to illustrate the effectiveness of the proposed containment control protocol.

Leaderless and leader‐following fixed‐time consensus for multiagent systems via impulsive control

SummaryThis article addresses the leaderless fixed‐time consensus (LLFTC) and leader‐following fixed‐time consensus (LFFTC) problems for multiagent systems (MASs) via impulsive control. First, a novel fixed‐time stability for impulsive dynamical system is developed. Then the novel fixed‐time impulsive control protocols are designed to achieve leaderless and leader‐following consensus for MASs. Based on the impulsive control theory, fixed‐time stability theory and algebraic graph theory, some sufficient conditions are derived for each agent to achieve LLFTC and LFFTC under the proposed control protocols. Finally, numerical simulations are put forward to validate the theoretical results.

Distributed H∞ containment control of multiagent systems over switching topologies with communication time delay

SummaryIn this study, we consider the problem of distributed H∞ containment control for multiagent systems over switching communication topologies. There exists a constant time‐delay and the energy‐bounded communication disturbances in the information transmission process, which are considered. Using the relative output, we develop an observer‐based containment control scheme such that the followers asymptotically converge to the convex hull formed by the leaders with a guaranteed H∞ performance level. By constructing a Lyapunov functional and using the inequality technique, sufficient conditions for the existence of such dynamic controllers are obtained in terms of linear matrix inequalities. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed control protocol.

Robust Time-Varying Formation Control for a Set of Quad-Copters With Switching Interaction Communication Topology

This article focuses on designing a robust time-varying formation controller for a set of micro quad-copters with switching interaction communication topology. Each micro quad-copter within the formation is represented by an under-actuated nonlinear model with the dynamics of each quad-copter being subjected to parameter perturbations and external disturbances. A robust formation control protocol is proposed that consists of a position controller and an attitude controller. The theoretical analysis is detailed to prove robust stability and tracking performance of the multi-vehicle control system, subject to uncertainties and switching interaction communication topology. Experimental and simulation results for a set of micro quad-copters validate the advantages of the proposed control protocol in time-varying formation flights.

Pull-Based Event-Triggered Containment Control for Multiagent Systems With Active Leaders via Aperiodic Sampled-Data Transmission

In this article, the containment control problem of multiagent systems (MASs) with active leaders under a directed communication graph is addressed. A novel pull-based event-triggered protocol combined with aperiodic sampled-data mechanism is first presented, where each agent merely updates controller at its own triggering instants. Under the proposed control protocols, the information is only exchanged and calculated at the aperiodic sampling instants, therefore, it can reduce communication congestion and save computing resources. Furthermore, the Zeno behavior is naturally excluded because the trigger instants are in the set of aperiodic sampled instants. By virtue of the algebraic graph theory and Lyapunov stability analysis, it is shown that the active leaders can reach their desired states predefined arbitrarily and all followers are driven to the convex hull formed by the leaders. Finally, an illustrative example is given to validate the theoretical results and emphasize the advantages of the proposed protocols.

Truncated prediction-based distributed consensus control of linear multi-agent systems with discontinuous communication and input delay

In this paper, distributed consensus control protocols are given for linear multi-agent systems with input delay under direct communication graphs. Compared with the multi-agent systems under continuous communication, there are more challenges in the consensus problems of multi-agent systems under discontinuous communication. Furthermore, the consensus of multi-agent systems with control input delay and discontinuous communication are much more similar to the practical engineering situation, which further increases the difficulties of consensus control. Based on these discussions, two consensus problems, including leader following case and leaderless case, are studied in this paper. A prediction of the system’s state information over the delay time is approximated by the zero input solution of the agent system model. We also propose a new discontinuous communication mode, which combines event triggered mechanism and a uniform quantization method. Unlike the existing discontinuous communication method, our proposed control protocols ensure that each agent decides when to transport its state information to its neighbors such that continuous communication between any two agents is no longer needed. In addition, through the non-smooth analysis of the closed-loop systems, the uniformly bounded consensus results are guaranteed, and the bound of the consensus error can be adjusted by choosing appropriate parameters.

Consensus Formation Control and Obstacle Avoidance of Multiagent Systems with Directed Topology

This study addresses the problems of formation control and obstacle avoidance for a class of second-order multiagent systems with directed topology. Formation and velocity control laws are designed to solve the formation tracking problem. A new obstacle avoidance control law is also proposed to avoid obstacles. Then, the consensus control protocol consists of the formation, velocity, and obstacle avoidance control laws. The convergence of the proposed control protocol is analyzed by a redesigned Lyapunov function. Finally, the effectiveness of theoretical results is illustrated by simulation examples. The simulation results show that the formation tracking problem of the given multiagent systems can be realized and obstacles can be avoided under the proposed control protocol.